U.S. patent application number 10/821157 was filed with the patent office on 2004-09-30 for propshaft assembly with vibration attenuation and assembly method therefor.
Invention is credited to Armitage, Mary Ellen, Heaton, Jeffrey N., Kurecka, Donald J., Schankin, David P..
Application Number | 20040192451 10/821157 |
Document ID | / |
Family ID | 27788314 |
Filed Date | 2004-09-30 |
United States Patent
Application |
20040192451 |
Kind Code |
A1 |
Armitage, Mary Ellen ; et
al. |
September 30, 2004 |
Propshaft assembly with vibration attenuation and assembly method
therefor
Abstract
A shaft structure and at least two non-identical inserts. The
shaft structure has a cavity and vibrates in response to the
receipt of an input of a predetermined frequency such that at least
two second bending mode anti-nodes are generated in spaced relation
to one another along the longitudinal axis of the shaft structure.
Each of the inserts is disposed within the longitudinally extending
cavity at a position that approximately corresponds to an
associated one of the anti-nodes. A method for attenuating noise
transmission from a vehicle driveline is also disclosed.
Inventors: |
Armitage, Mary Ellen;
(Kalamazo, MI) ; Heaton, Jeffrey N.; (White Lake,
MI) ; Schankin, David P.; (Harper Woods, MI) ;
Kurecka, Donald J.; (Rochester Hills, MI) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 828
BLOOMFIELD HILLS
MI
48303
US
|
Family ID: |
27788314 |
Appl. No.: |
10/821157 |
Filed: |
April 8, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10821157 |
Apr 8, 2004 |
|
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10097701 |
Mar 13, 2002 |
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6752722 |
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Current U.S.
Class: |
464/180 |
Current CPC
Class: |
F16D 2300/22 20130101;
Y10T 29/49774 20150115; F16C 3/023 20130101; B60K 17/22 20130101;
Y10T 29/49229 20150115; F16F 15/10 20130101; Y10T 29/49334
20150115; F16C 2326/06 20130101 |
Class at
Publication: |
464/180 |
International
Class: |
F16C 003/00 |
Claims
What is claimed is:
1. A propshaft assembly comprising: a shaft structure having at
least one cavity, the shaft structure vibrating in response to
receipt of an input of a predetermined frequency such that a pair
of second bending mode anti-nodes are generated in a spaced
relation to one another along a longitudinal axis of the shaft
structure; and two non-identical inserts disposed in the shaft
structure, each of the inserts being positioned at a respective one
of the anti-nodes, the inserts being configured to attenuate an
amplitude of vibrations at the anti-nodes.
2. The propshaft assembly of claim 1, wherein each of the inserts
is formed such that at least one of its density, mass, resilience
and length is different from that of the other insert.
3. The propshaft assembly of claim 2, wherein the inserts are
similar.
4. The propshaft assembly of claim 1, wherein at least one of the
inserts is press-fit into the shaft structure.
5. The propshaft assembly of claim 1, wherein at least one of the
inserts is formed from a foam.
6. The propshaft assembly of claim 5, wherein the foam is an
open-celled foam.
7. The propshaft assembly of claim 1, wherein the inserts are
similar.
8. A method for forming a propshaft assembly comprising: forming a
shaft structure; forming a first insert; forming a second insert,
the first and second inserts being non-identical; and inserting the
first and second inserts into the shaft structure in an axially
spaced-apart relation to one another.
9. The method of claim 8, further comprising determining a location
of a first bending anti-node and a second bending node along a
length of the shaft structure.
10. The method of claim 9, wherein the first insert is located at
the first bending anti-node and the second insert is located at the
second bending anti-node.
11. The method of claim 10, wherein each of the first and second
inserts has a length, a mass, a density and a resilience, and
wherein at least one of the length, the mass, the density and the
resilience of the first insert is different than that of the second
insert.
12. The method of claim 11, wherein at least one of the first and
second inserts is press-fit to the shaft structure.
13. The method of claim 12, wherein the first and second inserts
are similar.
14. The method of claim 8, wherein the first and second inserts are
similar.
15. A method for reducing vibration in a vehicle driveline
comprising: providing a shaft assembly with a shaft structure;
coupling the shaft structure to a power transmitting device, the
power transmitting device including a pair of meshing gears;
transmitting rotary power between the shaft assembly and the power
transmitting device, the meshing gears thereby generating gear mesh
vibration that is transmitted to the shaft assembly; determining a
location of a first bending anti-node and a second bending
anti-node along a length of the shaft structure; inserting a first
insert at the first bending anti-node; and inserting a second
insert at the second bending anti-node, the first and second
inserts being non-identical.
16. The method of claim 15, wherein each of the first and second
inserts has a length, a mass, a density and a resilience, and
wherein at least one of the length, the mass, the density and the
resilience of the first insert is different than that of the second
insert.
17. The method of claim 16, wherein at least one of the first and
second inserts is press-fit to the shaft structure.
18. The method of claim 16, wherein the first and second inserts
are similar.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a continuation of U.S. patent application Ser. No.
10/097,701 filed Mar. 13, 2002 entitled "Foam Lined Propshaft".
FIELD OF THE INVENTION
[0002] The present invention generally relates to noise attenuation
in vehicle drivelines and more particularly to an improved
noise-attenuating propshaft and a method for its construction.
BACKGROUND OF THE INVENTION
[0003] Propshafts are commonly employed for transmitting power from
a rotational power source, such as the output shaft of a vehicle
transmission, to a rotatably driven mechanism, such as a
differential assembly. As is well known in the art, propshafts tend
to transmit sound while transferring rotary power. When the
propshaft is excited a harmonic frequency, vibration and noise may
be amplified, creating noise that is undesirable to passengers
riding in the vehicle. Thus, it is desirable and advantageous to
attenuate vibrations within the propshaft in order to reduce noise
within the vehicle passenger compartment.
[0004] Various devices have been employed to attenuate the
propagation of noise from propshafts including inserts that are
made from cardboard, foam or resilient materials, such as rubber.
The inserts that are typically used for a given propshaft are
generally identical in their configuration (i.e., construction,
size, mass and density) and are installed in the propshaft such
that they are equidistantly spaced along the length of the
propshaft. Construction in this manner is advantageous in that it
greatly simplifies the manufacturer of the propshaft. Despite this
advantage, several drawbacks remain.
[0005] For example, symmetric positioning of the
identically-configured inserts within the propshaft typically does
not maximize the attenuation of the vibration within the propshaft.
Accordingly, it is desirable to provide an improved propshaft that
attenuates vibrations within the propshaft to a larger degree than
that which is taught by the prior art.
SUMMARY OF THE INVENTION
[0006] In one form, the teachings of the present invention provide
propshaft assembly with a shaft structure and two non-identical
inserts. The shaft structure has at least one cavity and vibrates
in response to receipt of an input of a predetermined frequency
such that a pair of second bending mode anti-nodes are generated in
a spaced relation to one another along a longitudinal axis of the
shaft structure. The inserts are disposed in the shaft structure
and are positioned at a respective one of the anti-nodes. The
inserts are configured to attenuate an amplitude of vibrations at
the anti-nodes.
[0007] In another form, the teachings of the present invention
provide a method for forming a propshaft assembly that includes:
forming a shaft structure; forming a first insert; forming a second
insert, the first and second inserts being non-identical; and
inserting the first and second inserts into the shaft structure in
an axially spaced-apart relation to one another.
[0008] In yet another form, the teachings of the present invention
provide method for reducing vibration in a vehicle driveline that
includes: providing a shaft assembly with a shaft structure;
coupling the shaft structure to a power transmitting device, the
power transmitting device including a pair of meshing gears;
transmitting rotary power between the shaft assembly and the power
transmitting device, the meshing gears thereby generating gear mesh
vibration that is transmitted to the shaft assembly; determining a
location of a first bending anti-node and a second bending
anti-node along a length of the shaft structure; inserting a first
insert at the first bending anti-node; and inserting a second
insert at the second bending anti-node, the first and second
inserts being non-identical.
[0009] Further areas of applicability of the present invention will
become apparent from the detailed description provided hereinafter.
It should be understood that the detailed description and specific
examples, while indicating the preferred embodiment of the
invention, are intended for purposes of illustration only and are
not intended to limit the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Additional advantages and features of the present invention
will become apparent from the subsequent description and the
appended claims, taken in conjunction with the accompanying
drawings, wherein:
[0011] FIG. 1 is a schematic illustration of an exemplary vehicle
constructed in accordance with the teachings of the present
invention;
[0012] FIG. 2 is a top partially cut-away view of a portion of the
vehicle of FIG. 1 illustrating the rear axle and the propshaft in
greater detail;
[0013] FIG. 3 is a sectional view of a portion of the rear axle and
the propshaft;
[0014] FIG. 4 is a top, partially cut away view of the
propshaft;
[0015] FIG. 5 is a schematic illustration of the maximum
displacement associated with the bending mode of the propshaft ;
and
[0016] FIG. 6 is a plot illustrating noise as a function of the
propshaft speed for three differently configured propshafts.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0017] With reference to FIG. 1 of the drawings, a vehicle having a
propshaft assembly that is constructed in accordance with the
teachings of the present invention is generally indicated by
reference numeral 10. The vehicle 10 includes a driveline 12
drivable via a connection to a power train 14. The power train 14
includes an engine 16 and a transmission 18. The driveline 12
includes a propshaft assembly 20, a rear axle 22 and a plurality of
wheels 24. The engine 16 is mounted in an in-line or longitudinal
orientation along the axis of the vehicle 10 and its output is
selectively coupled via a conventional clutch to the input of the
transmission 18 to transmit rotary power (i.e., drive torque)
therebetween. The input of the transmission 18 is commonly aligned
with the output of the engine 16 for rotation about a rotary axis.
The transmission 18 also includes an output 18a and a gear
reduction unit. The gear reduction unit is operable for coupling
the transmission input to the transmission output at a
predetermined gear speed ratio. The propshaft assembly 20 is
coupled for rotation with the output 18a of the transmission 18.
Drive torque is transmitted through the propshaft assembly 20 to
the rear axle 22 where it is selectively apportioned in a
predetermined manner to the left and right rear wheels 24a and 24b,
respectively.
[0018] With additional reference to FIGS. 2 and 3, the rear axle 22
is shown to include a differential assembly 30, a left axle shaft
assembly 32 and a right axle shaft assembly 34. The differential
assembly 30 includes a housing 40, a differential unit 42 and an
input shaft assembly 44. The housing 40 supports the differential
unit 42 for rotation about a first axis 46 and further supports the
input shaft assembly 44 for rotation about a second axis 48 that is
perpendicular to the first axis 46.
[0019] The housing 40 is initially formed in a suitable casting
process and thereafter machined as required. The housing includes a
wall member 50 that defines a central cavity 52 having a left axle
aperture 54, a right axle aperture 56, and an input shaft aperture
58. The differential unit 42 is disposed within the central cavity
52 of the housing 40 and includes a case 70, a ring gear 72 that is
fixed for rotation with the case 70, and a gearset 74 that is
disposed within the case 70. The gearset 74 includes first and
second side gears 82 and 86 and a plurality of differential pinions
88, which are rotatably supported on pinion shafts 90 that are
mounted to the case 70. The case 70 includes a pair of trunnions 92
and 96 and a gear cavity 98. A pair of bearing assemblies 102 and
106 are shown to support the trunnions 92 and 96, respectively, for
rotation about the first axis 46. The left and right axle
assemblies 32 and 34 extend through the left and right axle
apertures 54 and 56, respectively, where they are coupled for
rotation about the first axis 46 with the first and second side
gears 82 and 86, respectively. The case 70 is operable for
supporting the plurality of differential pinions 88 for rotation
within the gear cavity 98 about one or more axes that are
perpendicular to the first axis 46. The first and second side gears
82 and 86 each include a plurality of teeth 108 which meshingly
engage teeth 110 that are formed on the differential pinions
88.
[0020] The input shaft assembly 44 extends through the input shaft
aperture 58 where it is supported in the housing 40 for rotation
about the second axis 48. The input shaft assembly 44 includes an
input shaft 120, a pinion gear 122 having a plurality of pinion
teeth 124 that meshingly engage the teeth 126 that are formed on
the ring gear 72, and a pair of bearing assemblies 128 and 130
which cooperate with the housing 40 to rotatably support the input
shaft 120. The input shaft assembly 44 is coupled for rotation with
the propshaft assembly 20 and is operable for transmitting drive
torque to the differential unit 42. More specifically, drive torque
received the input shaft 120 is transmitted by the pinion teeth 124
to the teeth 126 of the ring gear 72 such that drive torque is
distributed through the differential pinions 88 to the first and
second side gears 82 and 86.
[0021] The left and right axle shaft assemblies 32 and 34 include
an axle tube 150 that is fixed to the associated axle aperture 54
and 56, respectively, and an axle half-shaft 152 that is supported
for rotation in the axle tube 150 about the first axis 46. Each of
the axle half-shafts 152 includes an externally splined portion 154
that meshingly engages a mating internally splined portion (not
specifically shown) that is formed into the first and second side
gears 82 and 86, respectively.
[0022] With additional reference to FIG. 4, the propshaft assembly
20 is shown to include a shaft structure 200, first and second
trunnion caps 202a and 202b, first and second insert members 204a
and 204b, first and second spiders 206aand 206b, a yoke assembly
208 and a yoke flange 210. The first and second trunnion caps 202a
and 202b, the first and second spider 206aand 206b, the yoke
assembly 208 and the yoke flange 210 are conventional in their
construction and operation and as such, need not be discussed in
detail. Briefly, the first and second trunnion caps 202a and 202b
are fixedly coupled to the opposite ends of the shaft structure
200, typically via a weld. Each of the first and second spiders
206aand 206b is coupled to an associated one of the first and
second trunnion caps 202a and 202b and to an associated one of the
yoke assembly 208 and the yoke flange 210. The yoke assembly, first
spider 206a, and first trunnion cap 202a collectively form a first
universal joint 212, while the yoke flange 210, second spider 206b
and second trunnion cap 202b collectively form a second universal
joint 214.
[0023] A splined portion of the yoke assembly 208 is rotatably
coupled with the transmission output shaft 18a and the yoke flange
210 is rotatably coupled with the input shaft 120. The first and
second universal joints 212 and 214 facilitate a predetermined
degree of vertical and horizontal offset between the transmission
output shaft 18a and the input shaft 120.
[0024] The shaft structure 200 is illustrated to be generally
cylindrical, having a hollow central cavity 220 and a longitudinal
axis 222. In the particular embodiment illustrated, the ends 224 of
the shaft structure 200 are shown to have been similarly formed in
a rotary swaging operation such that they are necked down somewhat
relative to the central portion 226 of the shaft structure 200. The
shaft structure 200 is preferably formed from a welded seamless
material, such as aluminum (e.g., 6061-T6 conforming to ASTM B-210)
or steel.
[0025] The first and second insert members 204a and 204b are
fabricated from an appropriate material and positioned within the
hollow cavity at locations approximately corresponding to the
locations of the second bending mode anti-nodes 230. The
configuration of each of the first and second insert members 204a
and 204b is tailored to the anticipated maximum displacement of the
shaft structure 200 at the anti-nodes 230 when the propshaft
assembly 20 is excited at a predetermined frequency and the insert
members 204a and 204b are not present. In this regard, the density,
mass and/or resilience of the first and second insert members 204a
and 204b is selected to provide a predetermined reduction in the
anticipated maximum displacement of the shaft structure 200 at the
anti-nodes 230.
[0026] In the example provided, the first and second insert members
204a and 204b are identically sized, being cylindrical in shape
with a diameter of about 5 inches and a length of about 18 inches.
The first and second insert members 204a and 204b are disposed
within the hollow central cavity 220 and engage the inner wall 228
of the shaft structure 200. Preferably, the first and second insert
members 204a and 204b engage the shaft structure 200 in a press-fit
manner, but other retaining mechanisms, such as bonds or adhesives,
may additionally or alternatively be employed.
[0027] The predetermined frequency at which vibration dampening is
based is determined by monitoring the noise and vibration of the
propshaft assembly 20 while performing a speed sweep (i.e., while
operating the driveline 12 from a predetermined low speed, such as
750 r.p.m., to a predetermined high speed, such as 3250 r.p.m.). In
the example provided, the first harmonic of the meshing of the
pinion teeth 124 with the teeth 126 of the ring gear 72 was found
to produce hypoid gear mesh vibration that excited the second
bending and breathing modes of the propshaft assembly 20 when the
propshaft assembly 20 was rotated at about 2280 r.p.m., as shown in
FIG. 5. As a result of the configuration of the propshaft assembly
20, the anticipated maximum displacement of the anti-node 230b is
shown to be significantly larger than the anticipated displacement
of the anti-node 230a, which is generated in a spaced relation from
anti-node 230b. Accordingly, if the first and second insert members
204a and 204b are not tailored to their respective anti-node 230,
noise attenuation may not be as significant as possible and in
extreme cases, could be counter-productive. As such, the first
insert member 204a is constructed from a material that is
relatively denser than the material from which the second insert
member 204b is constructed. In the embodiment shown, the first
insert member 204a is formed from a CF-47 CONFOR.TM. foam
manufactured by E-A-R Specialty Composites having a density of 5.8
lb/ft.sup.3, while the second insert member 204b is formed from a
CF-45 CONFOR.TM. foam manufactured by E-A-R Specialty Composites
having a density of 6.0 lb/ft.sup.3. The foam material is porous,
being of an open-celled construction, and has a combination of slow
recovery and high energy absorption to provide effective damping
and vibration isolation.
[0028] FIG. 6 is a plot that illustrates the noise attenuation that
is attained by the propshaft assembly 20 as compared with an
undamped propshaft assembly and a conventionally damped propshaft
assembly. The plot of the undamped propshaft assembly is designated
by reference numeral 300, the plot of the conventionally damped
propshaft assembly is designated by reference numeral 302 and the
plot of the propshaft assembly 20 is designated by reference
numeral 304. The undamped propshaft assembly lacks the first and
second insert members 204a and 204b but is otherwise configured
identically to the propshaft assembly 20. The conventionally damped
propshaft assembly includes a single foam damping insert that is
approximately 52 inches long and approximately centered within the
propshaft. The foam insert has a density of about 1.8 lbs/ft.sup.3
and provides a degree of dampening that is generally similar to
other commercially-available damped propshaft assemblies. Notably,
the propshaft construction methodology of the present invention
provides significant noise reduction at the predetermined frequency
as compared with the undamped and conventionally damped propshaft
assemblies.
[0029] While the invention has been described in the specification
and illustrated in the drawings with reference to a preferred
embodiment, it will be understood by those skilled in the art that
various changes may be made and equivalents may be substituted for
elements thereof without departing from the scope of the invention
as defined in the claims. In addition, many modifications may be
made to adapt a particular situation or material to the teachings
of the invention without departing from the essential scope
thereof. Therefore, it is intended that the invention not be
limited to the particular embodiment illustrated by the drawings
and described in the specification as the best mode presently
contemplated for carrying out this invention, but that the
invention will include any embodiments falling within the foregoing
description and the appended claims.
* * * * *